Naag

(Carboxy-peptidase II (Naaladase)

L-Glu

Figure 1. Synthesis of NAA and NAAG. Asp-NAT synthesizes NAA using acetyl CoA and L-aspartate in neuronal mitochondria. NAA possibly serves as a precursor of NAAG by peptide bond formation with L-glutamate, the enzyme catalyzing the reaction is yet to be described. NAAG is broken down by carboxy-peptidase II, localized to astrocytes, releasing NAA and L-glutamate. NAA is hydrolyzed by aspartoacylase localized to oligodendrocytes, releasing the acetate and L-aspartate.

(Carboxy-peptidase II (Naaladase)

L-Glu

Acetate

Figure 1. Synthesis of NAA and NAAG. Asp-NAT synthesizes NAA using acetyl CoA and L-aspartate in neuronal mitochondria. NAA possibly serves as a precursor of NAAG by peptide bond formation with L-glutamate, the enzyme catalyzing the reaction is yet to be described. NAAG is broken down by carboxy-peptidase II, localized to astrocytes, releasing NAA and L-glutamate. NAA is hydrolyzed by aspartoacylase localized to oligodendrocytes, releasing the acetate and L-aspartate.

The metabolism of NAA is summarized in Fig. 1. Asp-NAT synthesizes NAA using acetyl CoA and L-aspartate, most likely in neuronal mitochondria. NAA is proposed to serve as the precursor for the metabolite neuromodulator N-acetylaspartylglutamate (NAAG) synthesized by a yet to be described enzyme.28 Because the hydrolysis of NAAG by carboxypeptidase II (NAALADase) yields the products NAA and L-glutamate29,30, it has been hypothesized that the synthesis of NAAG could also occur by an enzyme catalyzed reaction, and preliminary observations are suggestive of an enzyme-

28,31,32

mediated synthesis. , , NAA is hydrolyzed by aspartoacylase, localized primarily in oligodendrocytes, producing acetate and aspartate.

Was this article helpful?

0 0

Post a comment